The delivery of gases is a significant processing step in the fabrication of semiconductor devices. Gases are delivered to process semiconductors using a variety of semiconductor fabrication equipment. In one such example, chemical vapor deposition (CVD) systems are used to convey certain gases which, via thermal reaction or decomposition, deposit a layer of material such as an oxide film on the surface of a semiconductor substrate or wafer.
One important component in many types of semiconductor fabrication equipment systems is the injector utilized for delivering gases to the substrate. In a CVD system for example, the gases must be distributed over the substrate so that the gases react and deposit a desirable film or layer at the surface of the substrate. One purpose of the injector is to convey the gases to a desired location in a controlled, and reproducible manner. Controlled distribution of the gases minimizes pre-mixing and prior reaction of the gases, and thereby maximizes the chance of substantially complete, efficient and homogeneous reaction of the gases. If the gas flow is uncontrolled, the chemical reaction will not be optimal and the result will likely be a film which is not of uniform composition and/or thickness. When this occurs, proper functioning of the semiconductor is impaired, and may even fail. Accordingly, it is desirable that an injector design promote the delivery of gases in a controlled and substantially uniform manner.
Given the importance of the injector, many types of designs have been developed. Two examples of prior art injector assemblies are described in U.S. Pat. Nos. 6,022,414 and 6,200,389, which are both incorporated herein by reference. Therein described is a single body elongated or linear type injector having multiple gas outlets extending along the length of the injector. Further described is an injector assembly having multiple injector heads formed within one block of material. While these injectors have shown to be an advantageous design, the manufacturing of the prior art multiple head single body injector assemblies are costly. The fabrication time is lengthy as each injector is machined (using wire EDM) sequentially in the same single billet of material.
For throughput, it is often desired to employ multiple injectors. When using a single body injector assembly, as the number of injector heads increases, so does the fabrication time. The lengthy fabrication time and high cost deters design iteration of the injector geometry which might improve overall process results. Further, there is increased liability during each successive fabrication step of placing the whole multiplicity of injector heads at risk with a single fabrication error. Accordingly, there is a need for an improved injector assembly that promotes easier fabrication and assembly.
In addition to the injector, an exhaust system, typically coupled to the injector assembly for removing the gases, also plays an important role in promoting substantially uniform and/or controlled delivery of gases to the substrate. There is continuous effort in the industry to develop improved exhaust systems, particularly systems which remove the gases in a substantially uniform manner. As the number of injectors increases, so does the complexity of the exhaust system and problems occur such as balancing of the exhaust gas flow. Since multiple injectors are desirable for increased throughput, there is a need for the development of improved exhaust systems as well.